Così fan tutte may well be the most ruthlessly, painfully true of all dramas. How could anyone ever have thought it superficial? Shocking, yes, but trivial? Even Tristan, devastating indictment of romantic love though it may be, succumbs to an extent to the glorification of that most destructive manifestation of the will to power: what Wagner, in correspondence, called Alberich's liebesgelüste. (Wagner was avoiding capitalisation of nouns during this 'revolutionary' period.) Così, by virtue of its highly contrived plot and development – Lorenzo Da Ponte knew precisely what he was doing – barely pretends at a false reconciliation, even, perhaps especially, at the very end. Mozart's ravishing music presents not a romantic utopia but rather how things really are. Its realism is truly shocking, all the more so given the aching beauty with which it is expressed. Where even most tragedies will flinch, this most sophisticated of comedies does not. Maybe Die Meistersinger, a far darker work than many realise, comes closest, yet it also does not depict the human condition quite so unsparingly as Così.

All of the singers impressed. Polenzani and Regazzo were both new to me, but acquitted themselves very well, both vocally and dramatically, with a sure command of line and style. As Ferrando, Polenzani matched a honeyed tone with just the right amount of virility, without ever descending into coarseness, as many tenors have been known to do in this role. Regazzo's vocal swagger was never overdone, but underlined the difference between him and his more reflective partner-in-deception. The Ferranese sisters were both well matched and well contrasted. Garança, with her appealingly creamy yet always secure tone, fully deserves the plaudits she has won. Röschmann, if a little less colourful, exhibited her expected fine command of Mozartian style. Rebecca Evans proved a refreshingly youthful, vigorous Despina, with nothing of the usual old maid about her: acting included, rather than precluded, singing. But the presiding genius on stage was Thomas Allen, whose portrayal, in whichever production I have seen him, now comes close to definitive. Watching, directing, manipulating, here is the supremely judged watchmaker – or at least he would be were there no conductor to consider.

For Sir Colin Davis's reading came as close to perfection as we may ever expect to hear. It might be foolish to say without reservation that this was his greatest performance of any work, but I should not hesitate to say that he has done nothing greater. I have never doubted that Mozart is the most difficult composer to perform well, not least since the perfection in his music requires that ever elusive perfection from the performer. The balance between every aspect of Mozart's requirements – melody, harmony, counterpoint, instrumentation, phrasing, articulation ... – is something in which Davis came as close to perfection as anyone since Karl Böhm. In his more recent Mozart performances, I have noticed a greater flexibility. This was certainly in evidence here, perhaps more so than in any performance of his I have yet heard. Some passages (e.g., during the Overture and Fiordiligi's Act II Aria, 'Per pieta') were taken daringly slowly, creating a magical stillness in which every heartbeat might be heard, and yet so perfectly that they never tipped into langour. Fleetness elsewhere was never purchased at the expense of that ruinous hard-driven quality that afflicts almost all 'period' or 'period-influenced' Mozart. Nor, I hardly need say, was there any of the alternate greyness and sourness exhibited by orchestras of that ilk. Instead, the Orchestra of the Royal Opera House came as close to usurping the Vienna Philharmonic's Mozart crown as any orchestra ever will. (And it should, of course, be remembered that on a bad day, and specifically with an inferior conductor, Viennese Mozart will fall far short of this.) Bubbling woodwind, the tenderly caressing horns of cuckoldry during 'Per pieta', strings silky almost beyond belief, kettledrum-playing that judged - again! - to perfection the weight required to underpin harmonic and rhythmic momentum: all this and more was there.

The problem, sadly, lay with the production. At least it does for me, for I seem to be almost the only person who dislikes it. Part of the difficulty I have with it is that it is not nearly so clever as it thinks it is, or rather as Jonathan Miller thinks it is. He is right to point to the work's artificiality. It is that, of course, which permits its utterly ruthless realism; such are dialectics. Yet the artificiality is not there for its own sake, but in order to further the realism. I have no especial problem with the panoply of gadgetry, not least those incessantly employed mobile telephones, although less would be so much more here. There is far too much playing 'for laughs': this comedy is not, any more than Le Misanthrope, low farce. Most of the audience seemed to love this, taking up any opportunity to laugh at the most innoportune moments. However, the great stumbling block for me, as it was the previous time I saw this production, is the presentation of Ferrando and Guglielmo in their 'Albanian' disguises. One can understand the impulse to portray them very differently from their initial, Gieves and Hawkes-clad state, although even the necessity for that is debatable. (In so artifical a work, might it not be all the more powerful to render them very close, or even identical, to how they have always been?) But to present them in the most unattractive way possible, to compel fine artists to act with utterly unconvincing loutish behaviour, to make anyone who cares to consider the matter wonder how on earth anyone, let alone our ladies from Ferrara, would give men of such bizarre and unbecoming appearance even a second glance: not only does this more than strain credulity, it cheapens this most sophisticated of works. Whatever was Miller thinking of? This could not detract too much from the sublimity of the musical performance. But what a shame...